1. Introduction
Handball is a demanding contact sport characterised by fast and dynamic games consisting of various types of movements such as running, jumping, sprinting, swinging, hitting, blocking, and pushing an opponent [
1]. Furthermore, various abilities such as speed, agility, endurance, and explosive power certainly play significant roles in the successful performance of handball players [
1,
2,
3]. In addition, the ability to throw is one of the most important skills in handball, and a successful throwing technique is determined by the precision and speed of the ball [
4,
5,
6]. Shooting precision and the speed of the ball are considered especially important factors which can influence the overall effectiveness of the throw in handball and, consequently, the end result of a game [
7,
8]. Accordingly, there are different strategies for making a goal-directed throw. The first one is to throw the ball as fast as possible with no intention to aim accurately, trying to surprise the defenders and goalkeeper and give them less time to react adequately and save the shot. The second strategy is to throw the ball as accurately as possible, trying to keep the ball out of reach of the goalkeeper. Certain authors point out that precision is more important, but if athletes focus mainly on precision, the speed of the ball decreases at the same time [
5,
7].
When discussing the velocity of shooting, the velocity of movement of the smaller and lighter parts of the body with lesser inertia is added to the velocity of the bigger parts. This enables achieving the greatest possible velocity at the end of the whole kinetic chain (each proximal part offers support for the more distal part). At the end of the overall movement pattern, the created energy transfers to the ball [
9].
To be successful, i.e., to score the goal, handball players use different throwing techniques based on their playing position. In addition, the chosen technique is also directly influenced by the movements of the defensive players. The aim of each attack is to try to ensure the optimal position for a shooter. This is achieved by using fast movements on the field in combination with various changes in the movement direction of the body, with or without the ball. It has been estimated that team handball players make approximately 48,000 throws in a season at a median throw speed of 130 km/h [
10], and from the wide variety of techniques used for shooting, the most common throw is a jump shot. It is considered that from the overall number of throws during the game, 73–75% are jump throws [
11]. Tuquet et al. [
12] have analysed the number of steps which players use before shooting at the goal. The authors provide that players use zero steps in 17.3%, one step in 26.4%, two steps in 31%, three steps in 22%, and more than three steps (rules violation–but not sanctioned by referees) in 2.3% of shots at the goal. This data shows that a one-step jump shot is very important in the handball match. Although there is not any concrete research about it, the aim of this research will show if this shot technique is neglected during the training of handball players. Most of the research concentrates on the three-step jump shot, which is believed as most common in handball, but the numbers above show different.
The basic jump shot in team handball involves the execution of a vertical jump of the contralateral leg following a three-step run-up [
13]. However, since the overall game of handball is developing constantly and rapidly in various segments, so is the performance of the jump shot. What is identical in each performance technique of the jump shot is that this way of shooting combines moving actions of cyclic and non-cyclical types, and those are running, jumping, and throwing. It has to be emphasised that the data regarding the precision of handball players are scarce, especially when discussing younger categories. Nevertheless, the success of shots, expressed as the goal shot efficiency or as the percentage of successful throws from the entire number of shots, is one of the most important factors that directly influence the results or outcomes of matches.
Several researchers have studied the relationship between the velocity of movement of the upper limb and throwing on-the-spot shot or jump shot performance in handball [
14,
15]. Furthermore, several studies suggest that jump height achieved during throws may also be considered one of the important determinants of successfully performed jump shots. A high jump is often in relation to a good position for throwing over the defenders’ block. This is especially emphasised when players shoot from the backcourt position or when they have more time to prepare a shot [
13,
16,
17].
Often, the attacker does not have a sufficient amount of time to prepare optimally for the upcoming shot, so the player has to adjust his actions in a way to execute the jump shot after only a one-step run-up. At the same time, this could possibly affect the players’ possibility to achieve the necessary jump height for throwing over the block of the defenders. In order to determine crucial parameters for effective and successful sports performance, it is necessary to conduct an analysis of various techniques of the jump shot, as it is considered to be the factor which directly influences the outcome of the handball game. One of the analyses which can give an insight into the characteristics of jump shot performance is kinematic analysis. Kinematic analysis of elements of specific sport-related motor behaviour and technique ensures important information, representing the basis for in-depth and precise knowledge and understanding of their actual structure [
14].
Regarding fast game situations, players should be able to maintain the speed and accuracy of the shot in different game conditions, such as the spot shot or jump shot from various distances and the number of steps during their approach to the goal. Therefore, it is necessary to evaluate various characteristics and abilities to perform at a high level in any situation during the game.
The main aim of this research is to analyse a kinematic model of two different variations of executing the jump shot, one performed after only a one-step run-up and the other performed after a three-steps run-up. It is hypothesised that there are differences in kinematic parameters, shot precision, and shot accuracy between one-step and three-step jump shots in handball. Data related to shoulder and wrist velocity, jump height, ball velocity, and shot precision are going to be obtained and discussed. It is especially important to discover potential differences in the mentioned variables and evaluate the mentioned two techniques because of their role in the final result of the handball game.
2. Materials and Methods
2.1. Confirmation of the Ethics Committee
Before measurements, respondents were informed of the testing protocol and research goals. Therefore, prior to the start of the overall testing procedure, the respondents and their legal guardians gave written consent for the testing protocol and for the use of their personal data. This research was approved by the Ethics Committee of the Faculty of Kinesiology, University of Zagreb, in accordance with the Declaration of Helsinki.
2.2. Measurement Protocol
The testing was performed on the first day of the national team preparation period. Prior to the testing protocol, the players were informed of the tasks which they were required to perform. In addition, a demonstration of each shot was presented. Before the warm-up protocol, basic anthropometric and morphological measurements were taken. The warmup protocol consisted of in-line running, dynamic stretching drills, ball handling, passing drills, and 5 trials of shot per task. Moreover, a predefined calibration of the kinematic suit was performed, and players were asked to start with the shooting procedure. Each player performed 6 shots with a one-step run-up and 6 shots with a three-steps run-up from their position. Firstly, players were asked to target the upper opposite corner (3 shots) and, after that, the lower opposite corner (3 shots). Between each shot, there was a 15 s rest phase to recover from the previous shot and to prepare for the next one.
2.3. Participants
The respondents (N = 27) included in this research were female Croatian national handball team players (U17 N = 15 and U19 N = 12). The players were averagely aged 16.77 ± 1.10 years, with body height (H) of 170.29 ± 15.62 centimetres, body weight (W) of 64.62 ± 6.77 kg, and an average fat percentage (% BF) of 21.68 ± 3.29%. As all the players are competing at the highest competition level, the main inclusion criterion was the related health status (no injury in the last 6 months) and playing position (wing and back players). The respondents did not play any matches 3 days prior to the testing and had a reduced training volume and intensity.
2.4. Materials
The Tanita RD-545 (BIA—Bioelectrical Impedance Analysis) scale was used to determine the basic morphological characteristics (body weight, % of body fat, and BMI-Body Mass Index) of the respondents. The Seca 213 portable measuring device was used to measure body height. The kinematic system (Xsens, Movella, CA, USA) was used for the observation of the kinematic parameters of shots. The system was set to record at 60 Hz frequency, 30 ms latency, and 1000 Hz sampling rate. The Xsens MVN (v.2022.0.2) software package was used to record and analyse the performance of shots. A kinematic suit consists of 17 non-invasive sensors that are placed on the respondents’ bodies in a predefined protocol. Previous research [
18,
19,
20] determined the metric characteristic and possibility of measuring kinematic parameters with the Xsens system in sports games and in handball. Elastic straps were used to define targets on the goal (upper and lower opposite corners). Targets were set in corners of the goal 50 cm from the end post in a horizontal and vertical direction and connected with elastic straps [
21]. For accuracy, there were scores for every jump shot performed. If the respondent missed the target or edges of the target, it was 0 points. For every shot hitting the bar or post along with the elastic strap, the participant obtained 1 point. Hitting the target inside the bar, post, and elastic strap was 2 points (also 2 points if the ball bounces off mentioned edges into the target). The Stalker speed radar (Stalker ATS II, manufacturer: Stalker Sport, Richardson, TX, USA) was used for measuring ball speed (IHF official ball size 3). Illustration of target setting on the upper goal post in
Figure 1.
2.5. Variables Sample
The kinematic parameters observed in this research were divided into shots performed in the upper opposite (UO) and lower opposite (LO) goal target. Regarding the shot direction, the following variables were analysed: hand velocity (Hand_V); hand height reached (Hand_H); jump height (Jump_H); shoulder velocity (Sh_V); accuracy of the shot (Acc); and ball velocity/shot speed (V_ball). All kinematic values used for further analysis were maximum values obtained during each performed shot.
2.6. Statistical Analysis
The basic descriptive parameters (
Table 1) were calculated for all the observed variables. Normality of distribution was tested by using the Shapiro–Wilk test, and homogeneity of variances was tested by using Levene’s test. The data did not meet the criteria of normal distribution and homogeneity of variances, and based on the mentioned, non-parametric statistics were used to analyse the data. The Median test was used to determine the differences in obtained variables between one- and three-step run-ups. Effect size (η2) calculations (eta squared; small (η2 ≥ 0.01), medium (η2 ≥ 0.06), and large (η2 ≥ 0.14)) were used to estimate the magnitude of the results (differences between 2 run-ups techniques) and were reported as a measure of practical significance. A significance level was considered at the 95% confidence level for all statistical parameters. Moreover, Pearson’s chi-squared test was used to determine the differences in jump shot precision parameters.
3. Results
The basic descriptive parameters (arithmetic mean and standard deviation) of the measured variables were calculated and presented in
Table 2. Moreover, this table also presents the results of the conducted Median test in order to determine the differences in the measured variables between the two variations of jump shot performance. Statistically significant differences were determined in almost all of the measured variables, both when performing the shot in the upper opposite and the lower opposite angle of the goal. The only variable that did not differ is the hand height (
p = 0.43). Hand velocity was greater when performing the three-step run-up before the jump shot when aiming at both the lower and upper opposite angles (
p < 0.001). When observing the values of shoulder velocity, greater values were determined in jump shots after the three-step run-up (
p < 0.001). Consequently, the shot speed, i.e., the ball velocity, was greater after the three-step run-up when compared to after the one-step run-up (Upper opposite—73.70 km/h vs. 71.32 km/h; Lower opposite—76.43 km/h vs. 73.75 km/h). The mentioned differences are statistically significant (Upper opposite—
p = 0.04; Lower opposite—
p < 0.001). Furthermore, jump height was significantly higher when performing the three-step run-up (
p < 0.001). Additionally, because of the higher jump, the hand height during shot performance after the three-step run-up was also higher, even though the differences were not significant in relation to the one-step run-up.
Frequency of jump shot precision from one-step and three-step shots (
Table 3) shows similar numbers in shooting targets in the upper opposite corner with 46 missed shots by one-step and 47 missed shots by the three-step jump shot. Players hit the rim of the target with 21 (one-step) and 19 (three-step) shots and hit the target with 14 (one-step) and 15 (three-step) shots. The shooting target in the lower opposite corner was missed 33 times; players hit the rim 19 times and hit the target 29 times (one-step). With a three-step jump shot, the target was missed 29 times; players hit the rim 16 times, and players hit the target 36 times.
When observing Pearson’s chi-squared test results (
Table 4), it can be concluded there are no differences in jump shot accuracy when comparing one- and three-step run-ups when aiming both upper and lower opposite targets.
4. Discussion
The main aim of this research is to analyse the kinematic model of two different variations of executing the jump shot, one performed after only one step in the preparation phase and the other performed after a three-step preparation phase (run-up). Significant differences were found in almost all the measured kinematic parameters (hand velocity, jump height, shoulder velocity, and ball velocity (shot speed)), both when performing the shot in the upper opposite and the lower opposite angle of the goal. The only variable that did not differ is the reached hand height. There is no difference in jump shot accuracy when comparing one- and three-step run-ups when aiming both upper and lower opposite targets. Results confirm that although a jump shot is an automated dynamic motor stereotype of movement in handball, a one-step jump shot is not included enough in the everyday training process as there are significant differences with the three-step jump shot in observed variables.
Shooting the goal in handball is one of the most important predictors of success in handball because the aim of the handball game is to score more goals than the opponent. Modern handball requires much greater technical and tactical readiness of both individual players and the team, and accordingly, tactical situations are developed in order to achieve a goal in the simplest possible way using one of the shooting techniques. The three most common shooting techniques in handball are the standing spot shot (the player keeps the standing foot on the floor), the standing shot with a run-up (the player’s foot is on the floor after the run-up) and the jump shot, which consists of a vertical jump of one leg at take-off after the three-step run-up [
22]. Therefore, the handball shot is one of the most studied and cited specific skills in team handball [
23,
24,
25], especially when discussing the three-step shot. In this paper, the difference between the kinematic parameters was observed during a shooting at the goal from one step and from three steps using the jump shot technique. The technique of shooting from one step was chosen for situations in the game where players sometimes do not have time for the classic jump shot from three steps. One-quarter of all goals in handball matches (26.4%) come from one-step shots on the goal [
12]. Examples of one-step jump shots: the left or right wing is waiting for a deflected or saved ball near the line that limits the goalkeeper’s space, in the position of a circle runner (pivot) in the same situation, or when the circle runner player receives the ball in the form of an assist. In addition, considering the situations in the game, the ball can be received by any outside player on the line, which limits the goalkeeper’s space. These are all situations where the player has no space to make a jump shot from the three-step run-up. A quick shot at the goal from outside positions from just one step is often expedient because it has an element of surprise for the goalkeepers, but also for the defensive players because they do not have time to react and prevent the shot on the goal.
Precisely because of the many situations on the field in which the one-step jump shot is used, the aim of this paper was to determine whether there is a significant difference in the kinematic parameters during shots on target with a one-step jump shot and a three-step jump shot. Differences were found in almost all the observed kinematic parameters that were selected for this research. The only difference which is not significant is the reached hand height. Differences in jump height are expected, considering that after a long run, a greater force is generated in reflection, and hand height reached is highly correlated with jump height, so the significance, in this case, is logical. The difference in hand velocity between one and three steps is unexpected because it is considered that the technique of shooting from one step compared to three steps is not impaired, but the results show us exactly the opposite. Given that it has been proven that the speed in the shoulder joint is related to the speed of throwing the ball and hand velocity [
20], the significance of the differences can be interpreted by the final velocity of the throwing. The velocity of throwing in handball is the result of successive actions of the kinematic chain, which affect the maximum speed of the throw. Significant levels of power and muscle strength are essential to achieve high shooting velocity, which can be achieved with regular everyday training activities and more experience [
21] containing repeated shooting motions. Given that this speed is significantly reduced when shooting at the goal from one step compared to three steps, it can be concluded that there is a decrease in the quality of the shooting technique. In addition, the effect size of the shooting speed is large for both targets aiming upper high and upper low, which can only confirm conclusions regarding shooting speed. When observing Pearson’s chi-squared accuracy test results in one- and three-step run-up jump shot, there is no significant difference, both in upper and lower opposite targets. It can be concluded that players already have their motion of the shot automated by aiming the target with the last part of the shot with the wrist, so their accuracy is not influenced by a number of steps in the preparation phase. The frequency of jump shot precision from one-step and three-step shots show similar numbers in shooting targets in the upper opposite corner, with 46 missed shots by one-step and 47 missed shots by the three-step jump shot. Players hit the rim of the target with 21 (one-step) and 19 (three-step) shots and hit the target with 14 (one-step) and 15 (three-step) shots. The shooting target in the lower opposite corner was missed 33 times; players hit the rim 19 times and hit the target 29 times (one-step). With a three-step jump shot, the target was missed 29 times; players hit the rim 16 times, and players hit the target 36 times. In order to maintain the shooting technique, i.e., so that shooting at the goal with a one-step jump shot is of the same quality and precision as shooting from three steps, it is recommended to include one-step jump shots in the training process. More specific training with shooting towards the target from one-step jump shots should be performed more continuously and more often from every playing position in handball.
The strength of this research lies in the fact that it is conducted with female U17 and U19 national team players as the best handball players at their age. However, this can also be considered a limitation, as this sample of respondents does not include the elite senior-level of handball players (although all of those players already compete at the senior level). Another limitation of the research could be in relation to the different positions of players, but this should not affect the results, as all players have a similar training mode with different kinds of shots being performed. Only during matches, players are mostly limited with shots to their positions in play, but this rarely goes over an average 10 shots per match. Future studies should include both female and male players from young age groups to elite-level players.